CCB-Center for Chemistry and Biomedicine, Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, 6020 Innsbruck, Austria.
Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
Molecules. 2021 Nov 10;26(22):6779. doi: 10.3390/molecules26226779.
Mid-infrared (MIR) and near-infrared (NIR) spectra of crystalline menadione (vitamin K) were measured and analyzed with aid of quantum chemical calculations. The calculations were carried out using the harmonic approach for the periodic model of crystal lattice and the anharmonic DVPT2 calculations applied for the single molecule model. The theoretical spectra accurately reconstructed the experimental ones permitting for reliable assignment of the MIR and NIR bands. For the first time, a detailed analysis of the NIR spectrum of a molecular system based on a naphthoquinone moiety was performed to elucidate the relationship between the chemical structure of menadione and the origin of the overtones and combination bands. In addition, the importance of these bands during interpretation of the MIR spectrum was demonstrated. The overtones and combination bands contribute to 46.4% of the total intensity of menadione in the range of 3600-2600 cm. Evidently, these bands play a key role in shaping of the C-H stretching region of MIR spectrum. We have shown also that the spectral regions without fundamentals may provide valuable structural information. For example, the theoretical calculations reliably reconstructed numerous overtones and combination bands in the 4000-3600 and 2800-1800 cm ranges. These results, provide a comprehensive origin of the fundamentals, overtones and combination bands in the NIR and MIR spectra of menadione, and the relationship of these spectral features with the molecular structure.
采用量子化学计算方法，对结晶甲萘醌（维生素 K）的中红外（MIR）和近红外（NIR）光谱进行了测量和分析。计算是在晶体点阵的周期性模型的谐波方法和单分子模型的非谐 DVPT2 计算的帮助下进行的。理论光谱准确地重建了实验光谱，从而可以可靠地分配 MIR 和 NIR 带。首次对基于萘醌部分的分子体系的 NIR 光谱进行了详细分析，以阐明甲萘醌的化学结构与泛频和组合带的起源之间的关系。此外，还证明了这些带在解释 MIR 光谱时的重要性。泛频和组合带对甲萘醌在 3600-2600cm 范围内的总强度的贡献为 46.4%。显然，这些带在塑造 MIR 光谱的 C-H 伸缩区域中起着关键作用。我们还表明，没有基频的光谱区域可能提供有价值的结构信息。例如，理论计算可靠地重建了 4000-3600 和 2800-1800cm 范围内的许多泛频和组合带。这些结果提供了甲萘醌的 NIR 和 MIR 光谱中基频、泛频和组合带的综合起源，以及这些光谱特征与分子结构的关系。
